After uninstalling Java, have you spotted Java related Java Deployment Toolkitplugin in Firefox?, Yes, Java Uninstaller not removed this one, don’t know why? These are annoyances users need to cope with Java and other software. If you install a program, that installs plugins and add-ons, its uninstaller should also remove them during it’s uninstall, is it not? Once this exists without Java on our systems knowing the use and purpose of it is not necessary. If you want to remove this plugin from Firefox, you’ve to follow the below procedure.

Note: Even with Java in use, you can remove this plugin, it is not necessary.

I had a similar problem with this JDT.
I had completely uninstalled Java on my computer and after reboot Firefox would still display the plugin JDT. What was odd though is that the version for the JDT was old (6.33) compared to the Java version (7u45)
So I followed the instructions here and couldn’t find the npdeployJava1.dll file in the windows\system32

I found one in C:\Program Files\java\jre7\bin\dtplugin, I removed it but it would still appear in the plug-in list of Firefox.

Therefore, I did a system wide search on the file and found out the there was a copy of the file in C:\Windows\SysWOW64
That that one was the culprit.

So if you have this problem and a Win7 64bit install check also this folder.

Windows 8 64
– Closed Firefox
– Uninstalled Java after which I had no Java directories in “Program Files” or “Program Files (x86)”
– I did a search, but didn’t find the file.
– I navigated to C:\Windows\System32 and the file was there, so find didn’t fine it. I made a directory above the directory named 1-Manually_Removed_Files, and moved deployJava1.dll and npdeployJava1.dll into it.
– I went into C:\Windows\SysWOW64 and found the file in there. I made a directory there also named 1-Manually_Removed_Files, and moved deployJava1.dll and npdeployJava1.dll into it.
– Started Firefox and the plugin no longer showed up.

I’ve had the ‘Java Deployment Toolkit’ on my Laptop for ages, and never actually got past just disabling it, so if I do get there (with the help of notes on this page – this is how I did it!). If I DO manage it, most of you should be capable tbh!
NB: Doing the Search/1st method did NOT work for some reason!

Using Windows 8 (not yet updated to 8.1), with Firefox – fully updated.
1. Open Library.
2. Go to ‘Computer’, followed by ‘C:’ > ‘Program Files (x86)’ > ‘Java’ > ‘jre7′ > ‘bin’ >
‘dtplugin’. (C:\Program Files (x86)\Java\jre7\bin\dtplugin)
(Note: There was no Java Folder in my ‘standard’ Program files.)
3. You will probably see 2 files here (or 1 if you no longer have Java installed):
deployJava1.dll
npdeployJava.dll = the hated file!
4. In this folder I created another folder named ‘Unwanted files’ (basically, keep a copy with a different address, so if it all goes horribly wrong…).
5. Move the ‘npdeployJava1.dll’ into this new folder, BUT if you still use Java, leave the ‘deployJava1.dll’ where it is! (When you go to move the file, it brings up a box to check (Admin) – but this does make it clear which one the deployment toolkit is.)
6. Checking it: Just by refreshing the Add-on Manager (Tools > Add-ons), in Firefox showed me that it had removed the vulnerable ‘Java Deployment Toolkit’, without even needing to re-start Firefox. (Also tested with re-start.)
Yet ‘Java’ itself (‘Java(TM) Platform SE 7 U51 10.51.2.13′ in my case!) was indeed still showing.
7. Testing it: I then went to the Java test page (this link is also the one to find and remove older versions as well, so if you wish to keep an Older Java, use the ‘Verify’ link further below), at https://java.com/en/download/uninstallapplet.jsp – which also showed it as being up-to-date, with no old versions. As well as the ‘Verify Java page’ https://java.com/en/download/installed.jsp?detect=jre.

So far, this seems to be doing the job. I’ve left the new folder (and old file) there for now (just in case!), but all seems to be going well!
Many thanks for all of the tips that enabled me to get rid of it, and maybe I’ll have included something, that will help someone else with this annoying piece of software!

Em “Icklem,” Using the wisdom in your post I was able to easily slay “the hated file.” You can see from the reader log how many prior suggestions failed and I didn’t notice any below yours — that’s where the genius resides. Thanks.
Bobby D
P.S. I deleted it directly without creating a safety folder

Mikee, please check the update (November one) posted at the bottom of the article before replying to the comments. If you uninstall Java, now that plugin will also be removed from Firefox, isn’t that happening for you in Windows 8.1?

Before tinkering with anything in the Windows Registry, it is always a good idea to right-click on the key heading, then select “Export.” Additionally, while naming/saving the export, add “.txt” as the extension. If anything messes up, remove the “.txt” extension, and click on the exported file to replace the original keys. Microsoft advises that setting a System Restore Point before editing the registry is preferable; the above is more of a targeted system restore point.

Delete this key, and only this key, at the following location:
HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins\@java.com/DTPlugin,version=10.17.2